A Ka Band Balanced Third LO-Harmonic Mixer Using a Lumped-Elements Quadrature Hybrid

A novel configuration of a subharmonic mixer utilizing third local oscillation (LO) harmonic is presented. The mixer is capable of down-converting a Ka-Band radio frequency (RF) signal with the third harmonic of an X-band LO signal to produce a 2 GHz intermediate frequency signal. It is fabricated on a 4 mil substrate using a 0.15 mum GaAs PHEMT process. A novel quadrature hybrid is realized by using compact lumped elements, and it is beneficial for the reduction of chip size for an LO at a relatively low frequency in this topology. This is because it does not need any bulky via holes. Compared with published subharmonic mixers, it provides a more flexible requirement for an LO source at a relatively low frequency for an overall communication system design. The measured results show that the best conversion loss is about 13.2 dB at a RF frequency of 29 GHz as a 10.5 dBm 9 GHz LO signal is pumped. The chip area of the mixer is less than 3.14 mm².